I am not sure why you would pull in a morphing RSS feed and then rewrite all the posts - it kinda defeats the object of the feed (either hand-write them from scratch to start with or leave them to morph on their own), but anyway . . .
I would suggest you speak to Cyber, he's the blog / RSS expert and is REALLY helpful. He has a product called
CyberSEO Suite which is a better version of FeedWordPress. It comes with free support and he is as good as it gets when it comes to blogs / RSS feeds so you can't go wrong. You can say I recommended you as I use his products and he has given me some invaluable help over the years.
His contact details are on the website.